Stratified sulfatometallates: unlocking a new dimension in sulfatomolybdates

Thus far, only a few sulfatomolybdates are known. Their anions feature mainly low dimensionalities. By choosing appropriate reaction conditions, new compounds, namely, β-K₂[MoO₂(SO₄)₂] and Na₂[MoO₂(SO₄)₂], are synthesised, which revealed layered structures for the first time for this class of materials. These compounds comprise sulfate tetrahedra and molybdate octahedra connected via common edges, forming a vierer ring between the building units. While the potassium cations are fully ordered in β-K₂[MoO₂(SO₄)₂], the sodium cations exhibit disorder in Na₂[MoO₂(SO₄)₂], which does not order at higher temperatures. Additionally, the compound crystallises in an incommensurate modulated structure at room temperature, which orders at higher temperatures. The titled compounds were characterised by single-crystal and powder XRD, MAPLE calculations, FT-IR spectroscopy, UV-vis spectroscopy, magnetic susceptibility analysis and thermogravimetric analysis (TGA). The latter reveals fairly high thermal stabilities for both compounds.